Conventionally, there are various electric device systems including a plurality of electric device units. There is well known an electric device system including the plurality of electric device units, which are electrically connected to each other by assembling the electric device units in line along a predetermined direction. A remote terminal device (hereinafter, also simply referred to as a remote terminal device) of a Programmable Logic Controller (PLC) can be cited as a typical example of the electric device system having the configuration.
The remote terminal device includes a communication unit and one or more I/O unit that can conduct communication with the communication unit through a serial bus line and a unidirectional communication line, and the communication unit and the I/O unit are generally formed into a building block type such that the I/O units are provided in the communication unit while continuously connected to each other.
For example, JP 6-6051 A, JP2001-217016 A, and JP 2012-182412 A disclose the remote terminal device having the configuration.
Frequently, each of the communication unit and I/O unit, which are of the electric device unit, is attached to an attaching rail such as a DIN (German industry standard) rail, and the adjacent electric device units are assembled so as to be engaged with each other.
In such cases, generally a guide groove and a projecting streak that are of a guiding mechanism are provided in a pair of electric device units adjacent to each other, and the projecting streak provided in one of the pair of electric device units is slidably guided by the guide groove provided in the other, whereby the pair of electric device units are detachably engaged with each other. For example, JP2001-217016 A and JP 2012-182412 A disclose the electric device unit in which the guiding mechanism is provided.